Polyelectrolyte membranes, such as perfluorosulfonated ionomers (U.S. Pat. Nos. 4,433,082; 5,422,411; 6,100,324), sulfonated poly(ether ether ketone), sulfonated poly(ether ether ketone) (Bishop M T, Karasz F E, Russo P S, Langley K H, Macromolecules, 18, 86 (1985)), and poly(benze imidazole) (U.S. Pat. Nos. 5,091,087; 5,525,436; 6,042,968) are materials of considerable commercial significance because of their use as solid polymer electrolytes in fuel cells and other applications in electrochemistry, separation technology, and a variety of electrochemical process and devices including chlor-alkali cells. High ionic conductivity is one of the important requirements for the application of polyeletrcolyte membranes in fuel cells. Lots of researchers have reported methods of improving the conductivity by chemical modification (Rikukawa M and Sanui K, Prog. Polym. Sci., 25, 1463 (2000)) or inserting inorganic oxides into ionic aggregation regions of polyeletrcolyte membranes (U.S. Pat. Nos. 5,523,181 and 5,766,787).
One of the most widely used polyelectrolytes in the application of proton exchange membrane fuel cells is perfluorosulfonated ionomer membrane. Phase separation between the hydrophobic component and the hydrophilic ionic groups happens in perfluorosulfonated ionomer membranes, which is heterogeneous on nanometer scale (Rubatt L, Gebel G, Diat O, Macromolecules, 37, 7772 (2004)). It is believed that the nano-structure of ionic aggregates is strongly correlated with proton transport properties of membranes. Thus to control the morphology and nano-structure of ionic aggregations is one of the methods to improve the ionic conductivity of polyelectrolyte membranes. In literature, it has been reported that the nano-structure of block copolymers can be aligned using an electric field (Amundson K, Helfand E, Davis D D, Quan X, and Patel S S, Macromolecules, 24, 6546 (1991)); (Morkved T L, Lu M, Urbas A M, Ehrichs E E, Jaeger H M, Mansky P, and Russel T P, Science, 271, 931 (1996)).